What Is the Difference Between 706 and 862 Heads?

Having the right automotive parts is crucial for the performance of any vehicle. However, many people get confused when choosing more specific parts like cylinder heads. Chevy engines, in particular, have several parts variations that can work on the same engine.

If you’re looking for a cylinder head for your chevy engine, you’ll have the option to choose between the 317, 862, or 706 heads. The 317 have superior ports but end up with a net horsepower loss. However, the 706 and 862 heads seem almost identical.

So, what’s the difference between these two cylinder heads, and which one is best for your engine? Read on to find out.

What’s Similar Between 706 and 862 Heads? 

Since most people think the two heads are identical, let’s first look at what makes them similar. Both the 706 and 862 cylinder heads have the following features in common:

  • Usage: Both heads can be fitted on the same engines.
  • Valve size: 317 heads have larger valves, but the 706 and 862 heads have almost identical valves.
  • Port size is identical in both.
  • Chamber cores are the same.

As you can see, there are no significant differences between the CNC ported 862 LS heads and the Chevy 862 LS heads. So if you’re not specific about your engine performance, you can choose either cylinder head.

However, if you’re the type of person who notices the slight differences in performance, knowing the difference between these two heads might help you choose the better one.

Differences Between the 862 and 706 Heads

The 706 and 862 cylinder heads have the following differences: 

  1. Casting Method

While both cylinder heads have almost identical casts, the process used to make each one is different. 862 heads are made using the sand casting method, which gives it the required durability. However, 706 heads are made using the Semi-Permanent Mold (SPM) method. This gives it a slight advantage over the 862 head.

Heads made using the SPM method have slightly higher durability. However, this is negligible compared to a solid 862 LS head. What affects the performance is the finishing smoothness and precision. 706 heads have a smoother surface finish, making them slightly more efficient.

So, while the casting method is often overlooked, it can make a difference in engine performance.

  1. Compression Ratio 

The compression ratio of the 862 head is slightly higher than that of the 706 head. This is caused by having a smaller combustion chamber and may also be affected by the deck milling. It’s also one of the main differences to consider when deciding between the two cylinder heads.

On the one hand, a smaller combustion chamber can generate slightly more engine power. This is why some people claim the 862 head enhances the engine. However, the smaller combustion chamber can also affect the clearance in the valves, so it’s worth keeping in mind.

In this sense, the 862 heads can give slightly better performance, but they are more likely to be troublesome in the long run. Yet, this difference is negligible, so most people will look at other factors such as price and availability when choosing between different engine types.

Which Cylinder Head is Best For Your Engine? 

When choosing a new cylinder head make, you should always look at performance, pricing, and long-term reliability. So let’s compare the 706 and 862 heads on these parameters:

  • Reliability 

862 heads are sand cast and will last longer than many other makes. However, SPM casting used in the 706 heads produces more consistent results. Also, the combustion chamber is smaller in the 862 head, which may cause clearance problems in the long run.

If you’re looking for long-term durability, then 706 cylinder heads are a slightly better option.

  • Pricing

Both cylinder heads are roughly the same price. The 862 is slightly more popular than the 706, but both are easily available. You shouldn’t have any issue adjusting either valve since they’re almost identical.

However, since the 706 head has a smoother surface finish, some people prefer porting the 862 head to improve the finish. When you factor in the cost of porting, the 862 head becomes slightly more expensive.

  • Performance

With a smaller combustion chamber, the 862 head gives slightly better power and fuel efficiency performance. However, the 706 head is designed to keep the optimal combustion ratio, which results in more consistent fuel efficiency. As a result, it will deliver slightly better fuel efficiency than the 862 head in the long run.

Final Thoughts 

Both then 706 and 862 cylinder heads are great options to use in your engine. With many similarities and minor differences, the average person will go for either. However, if you prefer slightly more engine power, go for the 862 head. On the other hand, if you prefer decent power, better long-term fuel efficiency, and more reliability, the 762 LP head is the better choice.

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